It has been found that various ore bodies, i.e., mineral deposits, cannot be economically mined using conventional mining methods. For example, a mineral deposit can be located at a sufficient depth or can contain such a low percentage of mineral values that the cost of using conventional mining methods is greater than the value of the minerals recovered.
One technique that has been used to recover mineral values from such deposits is in situ leaching. In an in situ leaching process, a liquid leach solution is generally provided to contact the minerals by downward percolation through the mineral deposit. The liquid leach solution extracts the minerals and provides a pregnant liquor which is pumped from the deposit to a recovery operation for recovery of mineral values.
One of the major problems encountered when using an in situ leaching technique is that generally the mineral deposit does not have the desired permeability for the leach solutions. For example, a deposit having a low permeability can result in a low rate of travel of leach solution through the deposit, thereby increasing the time and decreasing the rate at which mineral values are recovered. Also, when leaching values from a mineral deposit having a low or non-uniform permeability, the leach solution can bypass portions of the deposit, thereby reducing the amount of values extracted by the leach solution and resulting in a reduced yield from the process.
Attempts have been made to improve the process of leaching with liquid leaching solvents by increasing the permeability and porosity of mineral deposits.
For example, U.S. Pat. Nos. 3,822,916; 3,823,981; and 3,841,705 illustrate processes that use hydrofracturing or explosive techniques to increase the permeability and porosity of ore deposits prior to leaching the ore deposits with leach solutions. It has been found, however, that use of such fracturing and explosive techniques has not resulted in the desired permeability and porosity of ore deposits for efficient liquid leaching operations.
It is, therefore, desirable to provide a process which promotes increased permeability and porosity of an ore body for enhancing recovery of minerals when using liquid leach solutions.